System and method for variable geometry mechanism configuration

ABSTRACT

A system and a method for configuring at least one variable geometry mechanism (VGM) of an aircraft engine are provided. Pass-off testing data for the aircraft engine is obtained, the pass-off testing data indicative of an actual value of at least one operating parameter of the aircraft engine. Based on the pass-off testing data, at least one trim value to be used to adjust a setting of the at least one VGM to bring the actual value of the at least one operating parameter towards a target value is determined, a running line of the aircraft engine being substantially constant when the actual value of the at least one operating parameter is at the target value. The setting of the at least one VGM is adjusted, during pass-off testing of the aircraft engine, using the at least one trim value.

TECHNICAL FIELD

The application relates generally to controlling the operation ofengines, and more particularly to determining variable geometrymechanism (VGM) schedules.

BACKGROUND OF THE ART

Gas turbine engines for use in aircraft typically comprise a variablegeometry mechanism (VGM), such as inlet guide vanes (IGVs), whosevariable positioning may be controlled according to a schedule tooptimize compressor efficiency and minimize engine fuel burn. Knownsystems typically provide a common schedule amongst all engines, whichlimits engine operability and performance.

There is therefore a need for an improved system and method for variablegeometry mechanism configuration.

SUMMARY

In one aspect, there is provided a method for configuring at least onevariable geometry mechanism (VGM) of an aircraft engine. The methodcomprises obtaining pass-off testing data for the aircraft engine, thepass-off testing data indicative of an actual value of at least oneoperating parameter of the aircraft engine, determining, based on thepass-off testing data, at least one trim value to be used to adjust asetting of the at least one VGM to bring the actual value of the atleast one operating parameter towards a target value, a running line ofthe aircraft engine being substantially constant when the actual valueof the at least one operating parameter is at the target value, andadjusting, during pass-off testing of the aircraft engine, the settingof the at least one VGM using the at least one trim value.

In another aspect, there is provided a system for configuring at leastone variable geometry mechanism (VGM) of an aircraft engine. The systemcomprises at least one processing unit and a non-transitory computerreadable medium having stored thereon program code executable by the atleast one processing unit for obtaining pass-off testing data for theaircraft engine, the pass-off testing data indicative of an actual valueof at least one operating parameter of the aircraft engine, determining,based on the pass-off testing data, at least one trim value to be usedto adjust a setting of the at least one VGM to bring the actual value ofthe at least one operating parameter towards a target value, a runningline of the aircraft engine being substantially constant when the actualvalue of the at least one operating parameter is at the target value,and adjusting, during pass-off testing of the aircraft engine, thesetting of the at least one VGM using the at least one trim value.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a gas turbine engine, inaccordance with an illustrative embodiment;

FIG. 2 is a block diagram of the controller of FIG. 1 , in accordancewith an illustrative embodiment;

FIG. 3 is a graphical illustration of operability and performancecharacteristics of an engine before and after trimming, in accordancewith an illustrative embodiment;

FIG. 4 is a graphical illustration of operability and performancecharacteristics of a plurality of engines before and after trimming, inaccordance with an illustrative embodiment;

FIG. 5 is a graphical illustration of nominal and trimmed VGM schedulesof an engine, in accordance with an illustrative embodiment;

FIG. 6 is a block diagram of an example computing device, in accordancewith an illustrative embodiment;

FIG. 7A is a flow diagram of a method for determining a VGM schedule, inaccordance with an illustrative embodiment; and

FIG. 7B is a flow diagram of the step of FIG. 7A of determining at leastone trim value, in accordance with an illustrative embodiment.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

FIG. 1 illustrates a gas turbine engine 10 of a type preferably providedfor use in subsonic flight, generally comprising in serial flowcommunication a low pressure (LP) compressor section 12 and a highpressure (HP) compressor section 14 for pressurizing air, a combustor 16in which the compressed air is mixed with fuel and ignited forgenerating an annular stream of hot combustion gases, a high pressureturbine section 18 for extracting energy from the combustion gases anddriving the high pressure compressor section 14, and a lower pressureturbine section 20 for further extracting energy from the combustiongases and driving at least the low pressure compressor section 12.

The low pressure compressor section 12 may rotate independently from thehigh pressure compressor section 14. The low pressure compressor section12 may include one or more compression stages and the high pressurecompressor section 14 may include one or more compression stages. Acompression stage may include a compressor rotor, or a combination ofthe compressor rotor and a compressor stator assembly. In a multistagecompressor configuration, the compressor stator assemblies may directthe air from one compressor rotor to the next.

The engine 10 has multiple, i.e. two or more, spools which may performthe compression to pressurize the air received through an air inlet 22,and which extract energy from the combustion gases before they exit viaan exhaust outlet 24. In the illustrated embodiment, the engine 10includes a low pressure spool 26 and a high pressure spool 28 mountedfor rotation about an engine axis 30. The low pressure and high pressurespools 26, 28 are independently rotatable relative to each other aboutthe axis 30. The term “spool” is herein intended to broadly refer todrivingly connected turbine and compressor rotors.

The low pressure spool 26 includes a low pressure shaft 32interconnecting the low pressure turbine section 20 with the lowpressure compressor section 12 to drive rotors of the low pressurecompressor section 12. In other words, the low pressure compressorsection 12 may include at least one low pressure compressor rotordirectly drivingly engaged to the low pressure shaft 32 and the lowpressure turbine section 20 may include at least one low pressureturbine rotor directly drivingly engaged to the low pressure shaft 32 soas to rotate the low pressure compressor section 12 at a speedproportional to the low pressure turbine section 20 speed. The highpressure spool 28 includes a high pressure shaft 34 interconnecting thehigh pressure turbine section 18 with the high pressure compressorsection 14 to drive rotors of the high pressure compressor section 14.In other words, the high pressure compressor section 14 may include atleast one high pressure compressor rotor directly drivingly engaged tothe high pressure shaft 34 and the high pressure turbine section 18 mayinclude at least one high pressure turbine rotor directly drivinglyengaged to the high pressure shaft 34 so as to rotate the high pressurecompressor section 14 at a same speed as the high pressure turbinesection 18. In some embodiments, the high pressure shaft 34 may behollow and the low pressure shaft 32 extends therethrough. The twoshafts 32, 34 are free to rotate independently from one another.

The engine 10 may include a transmission 38 driven by the low pressureshaft 32 and driving a rotatable output shaft 40. The transmission 38may vary a ratio between rotational speeds of the low pressure shaft 32and the output shaft 40.

The engine 10 comprises one or more variable geometry mechanism (VGM),such as inlet guide vanes (IGVs) 42 moveable for directing air into thecompressor section 12 (e.g. compressor inlet guide vanes). For example,the IGVs 42 may comprise low-pressure compressor inlet guide vanes,mid-pressure compressor inlet guide vanes, and/or high-pressurecompressor inlet guide vanes. It should however be understood that theVGM may in some embodiments consist of outlet guide vanes for directingair out of the compressor section 12, variable stator vanes fordirecting incoming air into rotor blades of the engine 10, variablenozzles, handling bleed valves, and the like.

As described hereinabove, control of the operation of the engine 10 canbe effected by one or more control system, for example the controller200. The controller 200 can modulate a fuel flow (W₁) provided to theengine 10, the position and/or orientation (also referred to as a“setting”) of the VGMs within the engine 10, a bleed level of the engine10, and the like. In some embodiments, the controller 200 may beconfigured for controlling operation of multiple engines. For example,the controller 200 can be provided with one or FADECs or similardevices. Each FADEC can be assigned to control the operation of one ormore engine as in 10. Additionally, in some embodiments the controller200 can be configured for controlling operation of other elements of anaircraft (not shown) in which the engine 10 is operated, for instancethe aircraft's main rotor (not shown).

Although illustrated as a turboshaft engine, the gas turbine engine 10may alternatively be another type of engine, for example a turbofanengine, also generally comprising in serial flow communication acompressor section, a combustor, and a turbine section, and a fanthrough which ambient air is propelled. A turboprop engine may alsoapply. The engine 10 may also be an auxiliary power unit (APU), anauxiliary power supply), a hybrid engine, or any other suitable type ofengine. In addition, although the engine 10 is described herein forflight applications, it should be understood that other uses, such asindustrial or the like, may apply.

With reference to FIG. 2 , the controller 200 comprises an input unit202, a VGM trim determination unit 204, a VGM schedule determinationunit 206, and an output unit 208. It will be understood that theembodiment of FIG. 2 is merely one example of a configuration for thecontroller 200.

As will be described further below, the controller 200 is configured toconfigure the VGMs during pass-off testing by adjusting the settings(i.e. the position and/or orientation) of the VGMs based on a trimmedVGM schedule, in order to account for engine-to-engine variations inSurge Margin Audit (SMA) requirements to be met during pass-off testing.As used herein, the expressions “trimmed”, “trimming, and “trim” referto an adjustment or bias applied to a nominal or original value. As willalso be described further below, in order to target a substantiallyconstant running line for the engine 10, one or more trim values aredetermined by the controller 200 and applied to nominal VGM schedule(s)to obtain trimmed VGM schedule(s) which are used to adjust the settingsof the VGMs of the engine 10. As used herein, the expression “runningline” (also referred to as a “working line” or an “operating line”)refers to a typical steady state operating line of the engine 10 andprovides an indication of a locus (e.g., on a compressor map of theengine 10) of operating points of the engine 10 as it is throttled.Therefore, when a substantially constant running line is achieved forthe engine 10, the engine's operating points have a substantially equalvalue (e.g., within a predetermined tolerance) on a given axis (e.g.,x-axis or y-axis) of the compressor map. In other words, the engine'soperating points would be substantially positioned along a line(horizontal or vertical) on the compressor map.

The controller 200 determines the trim value(s) during a productionphase, and more particularly during pass-off testing, of each engine 10independently. As used herein, the expression “pass-off testing”, alsoreferred to as production (or repair/overhaul) pass-off testing oracceptance testing, refers to a phase during which an engine is tested(typically in a limited range of operating conditions vs. the fullengine operating envelope) to ensure that the engine meets keyacceptance criteria. The pass-off testing phase is the final check oncomponent manufacture and engine build quality upon engine assemblycompletion in production (or following repair and overhaul) and prior toshipment to a customer.

The determined trim value(s) are specific to each engine 10 (i.e.associated with the engine's serial number) and vary from engine toengine. In one embodiment, the engine 10 is operated under a testenvironment (e.g., in a production test cell provided at a testingfacility) to obtain the trim value(s) for that engine 10. Simulationand/or modeling of the engine 10 may also be used (e.g., through thecontroller 200) during the pass-off testing phase to obtain the trimvalue(s). The trim value(s) are determined to optimize one or moreparameters (also referred to herein as operating parameters) of theengine 10. Various parameters may apply because the definition of therunning line of engine 10 may vary (e.g., the running line may bedefined as a function of flow versus pressure ratio, engine rotationalspeed versus pressure ratio, engine power versus pressure ratio, enginerotational speed versus engine power, or the like). In some embodiments,the parameter to be optimized includes, but is not limited to, acompressor surge margin, a compressor stall margin, a compressorflameout margin, or any other suitable engine parameter. The compressor“surge margin” is a measure of how close an operating point of theengine 10 is close to surge (i.e. a complete disruption of the airflowthrough the compressor). Similarly, the compressor “stall margin” is ameasure of how close an operating point of the engine 10 is close tostall (i.e. a local disruption of the airflow in the engine'scompressor) and the compressor “flameout margin” is a measure of howclose an operating point of the engine 10 is close to flameout (i.e.run-down of the engine 10 due to the extinction of the flame in thecombustion chamber). In some embodiments, the trim value(s) are set toconcurrently optimize a plurality of parameters, such as fuel flow andpressure ratio (computed by dividing the engine's absolute outletpressure by the engine's absolute inlet pressure), or stall margin andTurbine Inlet Temperature (TIT). Optimization of three or moreparameters may also be performed. The VGM schedule is then trimmed basedon the trim value(s) during the pass-off testing phase of the engine 10,prior to shipment of the engine 10 to the customer.

The input unit 202 receives pass-off testing data for the engine 10. Thepass-off testing data may be obtained from a test cell system and/orretrieved from suitable storage (e.g., a memory or database)communicatively coupled to the controller 200, with pass-off testingbeing performed on a specific engine serial number with nominal VGMschedules. The pass-off testing data is therefore indicative of anactual value of the one or more operating parameters that are beingoptimized for the engine 10. In one embodiment, the pass-off testingdata is indicative of actual value(s) of an operability parameter of theengine 10 and actual value(s) of a performance parameter of the engine10. For example, the performance parameter may include, but is notlimited to, specific fuel consumption (SFC), turbine inlet temperature,and rotational speed of the engine, and the operability parameter mayinclude, but is not limited to, surge margin, pressure ratio, andacceleration time of the engine 10. As used herein, the term “specificfuel consumption” or SFC refers to the fuel efficiency of the engine 10with respect to power output, i.e. the mass of fuel needed to provide agiven output shaft power from the engine 10 for a given period.

The VGM trim determination unit 204 then determines, based on thepass-off testing data, at least one trim value to be used to adjust thesettings of the VGMs such that the actual value of the at least oneoperating parameter is brought towards a target value and asubstantially constant running line is achieved for the engine 10. Insome embodiments, the VGM trim determination unit 204 is configured todetermine the at least one trim value and reassess and adjust the atleast one trim value throughout the entire life of the engine 10, inorder to cater for engine deterioration. For example, the at least onetrim value (and/or the scaling factor described further below)determined during pass-off testing of the engine 10 could be reassessedbased on engine trend monitoring in the field.

The VGM trim determination unit 204 determines the at least one trimvalue by first obtaining (e.g., from any suitable storage means such asa database or memory) a virtual engine model that is able to simulatethe behaviour of the engine 10 based on the engine's design, operatingconditions, and limitations. The VGM trim determination unit 204 runsthe engine model at a target engine operating parameter, such as atarget compressor mass flow and pressure ratio. In some embodiments, theengine model is first aligned to match the pass-off testing data of thespecific engine serial number, as obtained from the input unit 202. TheVGM trim determination unit 204 may then run the aligned model at thetarget compressor mass flow and the VGM settings of the engine 10 may beadjusted to reach the target pressure ratio. It should be understoodthat the VGM settings may be adjusted to reach any other suitableparameter, such as a target surge margin for instance. The VGM setting(referred to herein as a “first VGM setting”) that allows to reach thetarget pressure ratio (or surge margin) at a given compressor mass flowmay then be recorded (e.g., stored in memory). The resulting shaft horsepower SHP (or corrected compressor rotor speed Ncorr, depending on theoperating parameter being targeted) may also be recorded. In someembodiments, the VGM trim determination unit 204 may subsequently runthe aligned model at the recorded shaft horse power (or correctedcompressor rotor speed), using the nominal VGM schedule and theresulting VGM setting (referred to herein as a “second VGM setting”) maythen be recorded. The at least one trim value may then be computed bythe VGM trim determination unit 204 by subtracting the first VGM settingfrom the second VGM setting. The at least one trim value may then berecorded by the controller 200.

The pass-off testing calibration is then repeated for the engine 10,where engine pass-off calibration is performed anew for the engine 10using the at least one trim value computed by the VGM trim determinationunit 204. New pass-off testing data is then received at the VGM trimdetermination unit 204 upon completion of this second pass-off testingphase. The VGM trim determination unit 204 then proceed to verify thatthe engine 10 is still within pass-off limits or requirements (alsoreferred to herein as “production acceptance limits” or criteria). Theproduction acceptance limits define an acceptance range (i.e. minimumand maximum values) for the engine operating parameters (e.g. fuelconsumption, turbine temperature, rotational speed of the engine) thatcannot be exceeded. The VGM trim determination unit 204 compares the newpass-off testing data (i.e. the actual values of the engine operatingparameters) to the production acceptance limits. When it is determinedthat the new pass-off testing data exceeds the production acceptancelimits, the VGM trim determination unit 204 adjusts the previouslydetermined trim value in order to bring the engine operating parameterswithin the production acceptance limits, thus optimizing the trim value.This adjustment process is repeated until it is determined that the newpass-off testing data is within production acceptance limits, in whichcase the VGM schedule trimming procedure is completed.

Once the trimming procedure is complete, the at least one trim value isthen sent from the VGM trim determination unit 204 to the VGM scheduledetermination unit 206, which applies the at least one trim value to oneor more nominal VGM schedules of the engine 10 to obtain one or moretrimmed VGM schedules. As will be described herein below, in someembodiments, the VGM schedule determination unit 206 applies the atleast one trim value to the nominal VGM schedule(s) directly (e.g.,linearly as a constant value). In other embodiments, the VGM scheduledetermination unit 206 determines a scaling factor to be applied to theat least one trim value in order to take account for additionalparameters (i.e. in addition to the optimized engine operatingparameter(s)) not quantified during engine pass-off. The additionalparameters may include, but are not limited to, altitude, ambientpressure, ambient temperature, engine speed, engine power, and airpressure measured at the exit of at least one compression stage of theengine 10. The scaled trim value(s) are then applied to the nominal VGMschedule(s) to obtain the trimmed VGM schedule.

The need for scaling the at least one trim value (and the manner inwhich the scaling factor is determined) may depend on the engine'ssensitivity to a plurality of factors and effects (e.g., altitude), aswell as on the VGM control schedule. For example, a VGM schedule that isalready catering for altitude effects may need little to no scaling(versus altitude), compared to a VGM schedule that does not takealtitude effects into consideration (i.e. does not perform anycorrection to cater for altitude effects). In addition, in someembodiments, the additional parameters may include other VGM schedules.For instance, the trim value(s) associated with a given VGM schedule(e.g., VGM₁) may be adjusted as a function of another VGM schedule(e.g., VGM₂), which may or may not be a trimmed schedule. For example,for VGM comprising a set of variable inlet guide vanes (VIGVs) and aHandling Bleed-off Valve (HBOV), the trim value(s) of the VIGVs may bescaled as a function of the HBOV schedule.

As mentioned herein above, the engine 10 may have one or morecompression stages operatively coupled to VGMs, a setting of which isdetermined based on a VGM schedule. In some embodiments, the VGMschedule determination unit 206 applies the at least one trim value totrim the VGM schedule associated with a single compression stage of theengine 10. In other embodiments, the VGM schedule determination unit 206applies the at least one trim value to trim the VGM schedules associatedwith multiple compression stages of the engine 10. In one embodiment,the VGM schedule determination unit 206 linearly applies (i.e. as aconstant value) the at least one trim value to the nominal VGM scheduleof one compression stage (e.g., the low pressure compressor section 12)and leaves the nominal VGM schedules of the remaining compression stages(e.g., the high pressure compressor section 14) untrimmed. In anotherembodiment, the VGM schedule determination unit 206 linearly applies theat least one trim value to the nominal VGM schedule of one compressionstage (e.g., the low pressure compressor section 12) and applies scaledtrim value(s) to the VGM schedules of remaining compression stages(e.g., the high pressure compressor section 14). Other embodiments mayapply.

The one or more trimmed VGM schedules are then sent by the VGM scheduledetermination unit 206 to the output unit 208 for the VGM settings to beadjusted. In one embodiment, the output unit 208 generates one or morecontrol signals based on the trimmed VGM schedule(s) to adjust thesettings of the VGMs for configuring the VGMs during pass-off. The oneor more control signals may be sent to an actuator system (e.g., one ormore hydraulic or electric actuators or any other suitable actuatingmeans) operatively coupled to the VGMs and configured to control aposition and/or orientation of the VGMs.

FIG. 3 illustrates the results of applying the systems and methodsdescribed herein to an engine, such as the engine 10 of FIG. 1 . FIG. 3is a graphical illustration of operability and performancecharacteristics of an engine, such as engine 10, before and aftertrimming, in accordance with an illustrative embodiment. Morespecifically, FIG. 3 shows a chart 300 of a performance parameter(horizontal or x-axis) versus an operability parameter (vertical ory-axis) of the engine 10. In one embodiment, the performance parameterof the engine 10 is SFC and the operability parameter of the engine 10is surge margin. As can be seen in FIG. 3 , when the engine's VGMschedule is untrimmed (i.e. the engine 10 is operated according to thenominal VGM schedule), the values (or operating points) 302 for surgemargin as a function of SFC are scattered throughout the chart 300, withthe surge margin values ranging between SM₁ and SM₂ for SFC valuesranging between SFC₁ and SFC₂. In contrast, when the engine's VGMschedule is trimmed using the system and methods described herein, theoperating points 304 for surge margin as a function of SFC remain(within a predetermined tolerance) at a substantially constant valuelabelled SM_(T) in FIG. 3 (also referred to herein as a target surgemargin value). The operating points 304 also remain within predeterminedproduction acceptance limits (i.e. requirements or criteria) illustratedby box 306 in FIG. 3 , unlike some of the operating points 302 whichexceeded the production acceptance limits. In other words, applying thetrim value to the nominal VGM schedule shifts the operating points ofthe engine 10 to target a balanced (i.e. substantially constant) runningline in terms of operability versus performance, within productionacceptance limits.

As described above, in one embodiment, the production acceptance limitsdefine an acceptance range (i.e. minimum and maximum values) for theengine operating parameters (i.e. performance and operabilityparameters) that cannot be exceeded. In other words, in the embodimentof FIG. 3 , the production acceptance limits (illustrated by box 306)include a minimum surge margin value SM_(min) below which the engine'ssurge margin cannot be decreased and a maximum surge margin valueSM_(max) above which the engine's surge margin cannot be increased. Inthe embodiment of FIG. 3 , The production acceptance limits also includea minimum SFC value SFC_(min) below which the engine's SFC cannot bedecreased and a maximum SFC value SFC_(max) above which the engine's SFCcannot be increased. As can be seen in FIG. 3 , for any SFC value, thetarget surge margin value SM_(T) achieved by trimming the VGM scheduleof the engine 10 using the systems and methods described herein remainswithin the production acceptance range, i.e. above the minimum surgemargin value SM_(min) and below the maximum surge margin value SM_(max).

Turning now to FIG. 4 , there is illustrated an example of applying thesystems and methods described herein to multiple engines each having aunique serial number associated therewith. FIG. 4 is a graphicalillustration of operability and performance characteristics of aplurality of engines before and after trimming, in accordance with anillustrative embodiment. FIG. 4 shows a chart 400 of a performanceparameter (horizontal or x-axis) versus an operability parameter(vertical or y-axis) for four (4) engines each having a respectiveserial number (S/N) associated therewith, the serial numbers beinglabelled from 1 to 4 in FIG. 3 for sake of clarity. While the chart 400is shown with respect to four (4) engines, it should be understood thatany suitable number of engines may apply. The initial (i.e. beforetrimming is applied) operating points of the engines are labelled 402 ₁,402 ₂, 402 ₃, and 402 ₄ and the trimmed operating points are labelled as402 ₁′, 402 ₂′, 402 ₃′, and 402 ₄′. The initial operating points 402 ₁,402 ₂, 402 ₃, and 402 ₄ are determined based on the pass-off testingdata obtained from each engine and are indicative of the actual valuesof each engine's operating parameters (i.e. performance and operabilityparameters). From FIG. 3 , it can be seen that all initial operatingpoints 402 ₁, 402 ₂, 402 ₃, and 402 ₄ are outside of the predeterminedproduction acceptance range defined by box 404 (i.e. fail to meet theproduction acceptance limits). As described herein above, the VGMschedule of each engine is trimmed in order to bring the actual valuesof each engine's operating parameters towards target operability andperformance values associated with a nominal engine (also referred to asan “average new engine” ANE), while meeting the predetermined productionacceptance limits. In other words, the VGM schedules are trimmed tobring the operating points 402 ₁, 402 ₂, 402 ₃, and 402 ₄ towards atarget operating point labeled as in 402 _(nominal) FIG. 3 . The targetvalues of the operating parameters (i.e. the target operating point 402_(nominal)) may be determined during engine design and may varydepending on engine configuration.

In one embodiment, the VGM schedule of each engine is trimmed bytargeting a given value O_(T) for an engine operability parameter, inorder to achieve a substantially constant running line. In oneembodiment, the operability parameter is surge margin. It should howeverbe understood that the definition of the running line may vary, asdescribed herein above, and the VGM schedule may therefore be trimmed bytargeting a given value for any other suitable operability parameter orby targeting a given value of an engine performance parameter.

Turning to the first engine, which has serial number 1 and an initialoperating point 402 ₁ (determined from the pass-off testing date for thefirst engine), it can be seen that the operability of the first engineis above (i.e. better than) that of the nominal engine while theperformance of the first engine is lower (i.e. worse) than that of thenominal engine. The trim value is then determined to bring the initialoperating point 402 ₁ towards the target operating point 402 _(nominal)while meeting the production acceptance criteria. More specifically,adjusting the setting of the first engine's VGM using the trimmed VGMschedule results in the initial operating point 402 ₁ being shifted to atrimmed operating point 402 ₁′, where the target operability (e.g.,surge margin) value O_(T) associated with the target operating point 402_(nominal) is achieved. It can be seen that, with the initial operatingpoint 402 ₁ shifted to the trimmed operating point 402 ₁′, theoperability of the first engine is lowered (yet achieves the targetvalue O_(T)) while the performance of the first engine is improved.

Turning to the second engine, which has serial number 2 and an initialoperating point 402 ₂, it can be seen that the operability of the secondengine is lower (i.e. worse) than that of the nominal engine while theperformance of the first engine is above (i.e. better than) that of thenominal engine. The trim value is then determined to bring the initialoperating point 402 ₂ towards the target operating point 402 _(nominal)while meeting the production acceptance criteria. More specifically,adjusting the setting of the second engine's VGM using the trimmed VGMschedule results in the initial operating point 402 ₂ being shifted to atrimmed operating point 402 ₂′, where the target operability value O_(T)is achieved. It can be seen that, with the initial operating point 402 ₂shifted to the trimmed operating point 402 ₂′, the operability of thesecond engine is improved while the performance of the second engine islowered (yet remains within the production acceptance range 404).

Turning to the third engine, which has serial number 3 and an initialoperating point 402 ₃, it can be seen that both the operability and theperformance of the third engine are lower (i.e. worse) than that of thenominal engine. The trim value is then determined to bring the initialoperating point 402 ₃ towards the target operating point 402 _(nominal)while meeting the production acceptance criteria. More specifically,adjusting the setting of the third engine's VGM using the trimmed VGMschedule results in the initial operating point 402 ₃ being shifted to atrimmed operating point 402 ₃′. It can be seen that, at the trimmedoperating point 402 ₃′, the target operability value O_(T) associated isnot achieved because this would result in the performance of the thirdengine failing to meet the production acceptance criteria (i.e.exceeding the minimum performance limit and in an operating point beingpositioned outside of the production acceptance range defined by box404). In other words, the minimum production performance acceptancelimit is reached before achieving the nominal operability target O_(T)and the maximum possible trim is reached at operating point 402 ₃′. Itcan be seen that, with the initial operating point 402 ₃ shifted to thetrimmed operating point 402 ₃′, the third engine's operability isimproved (although not achieving the target value O_(T)) while itsperformance is worsened (yet remains within the production acceptancerange 404).

Turning now to the fourth engine, which has serial number 4 and aninitial operating point 402 ₄, it can be seen that both the operabilityand the performance of the fourth engine are lower (i.e. worse) thanthat of the nominal engine. In fact, the fourth engine's operability andperformance are so far from the target values associated with operatingpoint 402 _(nominal) and from the production acceptance range 404 thatthe use of the systems and methods described herein cannot suffice tobring the operating parameters of the fourth engine within theproduction acceptance range 404. Indeed, when the trimmed schedule isused to adjust the setting of the VGMs of the fourth engine, the trimmedoperating point 402 ₄′ remains outside of the production acceptancerange 404. This may be indicative of a significant defect in the fourthengine. It may therefore be desirable to abort the trimming procedurefor the fourth engine (e.g., in order to avoid overcompensating foroverly deviated engine hardware and components) and prevent the fourthengine from being shipped to the customer. For example, the controller200 may output instructions to cause the fourth engine to bedisassembled and re-matched (i.e. have the VGM changed) prior toshipment. The controller 200 may therefore include logic to abort(and/or limit the range of) the VGM schedule trimming procedure forengines whose operating parameters remain, after trimming, beyond apredetermined threshold (e.g. for which the distance between theengines' operating points and the nominal operating point on thecompressor map exceeds a predetermined threshold distance), which isindicative of a defect of the engine. In other words, for such engines,the controller 200 may also cause the process of determining trimvalue(s) (as implemented by the VGM trim determination unit 204 of FIG.2 ) and determining trimmed VGM schedule(s) (as implemented by the VGMschedule determination unit 206 of FIG. 2 ) to be aborted. Alternativelyor additionally, the controller 200 may cause the trim value(s)determined by the VGM trim determination unit 204 to be limited to apredetermined value (e.g., ±5 to 10 degrees), depending on engine size,design, configuration, and the like. This may in turn avoid concealingpotential engine discrepancies.

Referring now to FIG. 5 , there is illustrated an example of trimmingapplied to VGM schedules in accordance with one embodiment. FIG. 5 is agraphical illustration of nominal and trimmed VGM schedules of anengine, such as the engine 10. The VGM schedules illustrated in FIG. 5represent the VGM position as a function of one or more parameters ofthe engine 10 and/or the aircraft. The parameters include the engineoperating parameter(s) to be optimized as well as additional parameters(which relate to the performance of the aircraft and/or the operatingenvironment of the aircraft) to be taking into account during VGMscheduling. The VGM schedules illustrated in FIG. 5 may therefore be afunction of engine and/or aircraft parameters that include, but are notlimited to, altitude, ambient pressure, ambient temperature, enginespeed, engine output shaft power (i.e. output shaft torque and speed),corrected compressor rotor speed, and compressor delivery air pressure.It should be understood that the VGM schedules may also be a function ofadditional parameters (e.g., specific work, corrected mass flow). Aspreviously noted, the VGM schedule trimming process is tailored to eachengine and the trim value, which is determined during production (i.e.during pass-off testing) of a given engine, may be proportionally scaledas a function of one or more of the engine and aircraft parameters todetermine a final trimmed VGM schedule. Scaling may be performed by thecontroller 200 as a function of a specific operating point in theenvelope at a given point in time.

For example, curve 502 illustrates a first nominal VGM schedule (VGMposition versus engine parameter) for the engine 10. Curve 502 may beused when the engine 10 is operating at zero (0) feet. The nominalposition for the VGM is set to POS₁ for a value PARAM₁ of the engineparameter. At POS₁, the trim value 504 ₁ is applied directly (e.g.linearly, as a constant value) to the nominal schedule 502. Applying atrim value 504 ₁ to the nominal schedule 502 shifts the VGM positionvertically to curve 506, which corresponds to a trimmed VGM schedule.For a same value PARAM₁ of the engine parameter, the trimmed VGMposition is POS₂. For other values (i.e. other than PARAM₁) of theengine parameter, the trim value 504 ₁ is scaled to obtain one or morescaled trim values (labelled 504 _(scaled)) that are applied to thenominal VGM schedule to obtain the final trimmed VGM schedule 506. Forexample, for a value PARAM₂ of the engine parameter, the trim value 504₁ is scaled to obtain a trim value 504 ₂ and the trimmed VGM position isshifted from POS₃ to POS₄. Curve 508 of FIG. 5 illustrates a secondnominal VGM schedule to be used when the engine 10 is operating at adifferent altitude (e.g., ten thousand (10,000) feet). It can be seenthat, for different values of the engine parameter, scaled versions ofthe trim value 504 ₁ (i.e. the scaled trim values 504 _(scaled)) areapplied to the second nominal VGM schedule to obtain the final trimmedVGM schedule illustrated by curve 510. The value of the scaling factorthat is applied to the trim value 504 ₁ varies depending on engineconfiguration, as discussed herein above.

In some embodiments, the controller 200 is implemented in one or morecomputing devices 600, as illustrated in FIG. 6 . For simplicity onlyone computing device 600 is shown but the system may include morecomputing devices 600 operable to exchange data. The computing devices600 may be the same or different types of devices. The controller 200may be implemented with one or more computing devices 600. Note that thecontroller 200 can be implemented as part of a full-authority digitalengine controls (FADEC) or other similar device, including electronicengine control (EEC), engine control unit (ECU), electronic propellercontrol, propeller control unit, and the like. Other embodiments mayalso apply.

The computing device 600 comprises a processing unit 602 and a memory604 which has stored therein computer-executable instructions 606. Theprocessing unit 602 may comprise any suitable devices configured toimplement the methods described herein such that instructions 606, whenexecuted by the computing device 600 or other programmable apparatus,may cause the functions/acts/steps performed as part of the methods asdescribed herein to be executed. The processing unit 602 may comprise,for example, any type of general-purpose microprocessor ormicrocontroller, a digital signal processing (DSP) processor, a centralprocessing unit (CPU), an integrated circuit, a field programmable gatearray (FPGA), a reconfigurable processor, other suitably programmed orprogrammable logic circuits, or any combination thereof.

The memory 604 may comprise any suitable known or other machine-readablestorage medium. The memory 604 may comprise non-transitory computerreadable storage medium, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Thememory 604 may include a suitable combination of any type of computermemory that is located either internally or externally to device, forexample random-access memory (RAM), read-only memory (ROM), compact discread-only memory (CDROM), electro-optical memory, magneto-opticalmemory, erasable programmable read-only memory (EPROM), andelectrically-erasable programmable read-only memory (EEPROM),Ferroelectric RAM (FRAM) or the like. Memory 604 may comprise anystorage means (e.g., devices) suitable for retrievably storingmachine-readable instructions 606 executable by processing unit 602.

With reference to FIG. 7A, there is illustrated an example method 700for determining a VGM schedule, in accordance with one embodiment. Atstep 702, pass-off testing data indicative of an actual value of atleast one operating parameter of the engine is obtained. As previouslydescribed, the pass-off testing data may be obtained from a test cellsystem and/or retrieved from suitable storage (e.g., a memory ordatabase). The next step 704 is to determine, based on the pass-offtesting data obtained at step 702, at least one trim value to be used toadjust the VGM setting to bring the actual value of the at least oneoperating parameter towards a target value for achieving a substantiallyconstant running line for the engine. The setting of that at least oneVGM is then adjusted using the at least one trim value (step 706). Aspreviously noted, step 706 is performed during pass-off testing.

Referring now to FIG. 7B, the step 704 of determining the at least onetrim value illustratively comprises obtaining (e.g., from any suitablestorage means such as a database or memory) a virtual model of theengine at step 802. As described herein above, the virtual engine modelis able to simulate the engine's behaviour based on the engine's design,operating conditions, and limitations. The next step 804 is to run theengine model to determine a VGM setting at which the actual value of theengine's operating parameter(s) is brought towards the target value. Inone embodiment, step 804 may first involve aligning the engine model tomatch the pass-off testing data obtained at step 702. Step 804 mayfurther involve running the aligned model at a target value for a firstengine operating parameter (e.g., a target compressor mass flow) andadjusting the VGM setting to reach a target value for a second engineoperating parameter (e.g., target pressure ratio or surge margin). Step804 may further involve recording (e.g., storing in memory) the VGMsetting (referred to herein as a “first VGM setting”) that allows toreach the target value for a second engine operating parameter at agiven value of the first engine operating parameter. The resulting shafthorse power SHP (or corrected compressor rotor speed Ncorr, depending onthe engine operating parameter being targeted) may also be recorded.Step 804 may further involve running the aligned model at the recordedshaft horse power (or corrected compressor rotor speed), using thenominal VGM schedule and recording the resulting VGM setting (referredto herein as a “second VGM setting”). The next step 806 is then todetermine the trim value based on the VGM setting as determined. In oneembodiment, step 806 involves computing the at least one trim value bysubtracting the first VGM setting from the second VGM setting.

At step 810, new pass-off testing data is obtained with the VGM settingbeing adjusted using the trim value determined at step 806. At step 812,it is assessed whether the engine operating parameter(s) are within aproduction acceptance range. As described herein above, the productionacceptance range defines minimum and maximum values (or limits) for theengine operating parameters that cannot be exceeded. The assessment isperformed at step 812 by comparing the new pass-off testing data (i.e.the actual values of the engine operating parameters) to the productionacceptance range. When it is determined that the engine operatingparameter(s) fail to be within a production acceptance range, the trimvalue determined at step 806 is adjusted to bring the engine operatingparameter(s) within the production acceptance range (814). Otherwise,the trim value determined at step 806 is retained (i.e. left unadjusted)and method 700 proceeds to step 706 for adjusting the VGM setting usingthe trim value.

The methods and systems described herein may be implemented in a highlevel procedural or object oriented programming or scripting language,or a combination thereof, to communicate with or assist in the operationof a computer system, for example the computing device 600.Alternatively, the methods and systems may be implemented in assembly ormachine language. The language may be a compiled or interpretedlanguage. Program code for implementing the methods and systems may bestored on a storage media or a device, for example a ROM, a magneticdisk, an optical disc, a flash drive, or any other suitable storagemedia or device. The program code may be readable by a general orspecial-purpose programmable computer for configuring and operating thecomputer when the storage media or device is read by the computer toperform the procedures described herein. Embodiments of the methods andsystems may also be considered to be implemented by way of anon-transitory computer-readable storage medium having a computerprogram stored thereon. The computer program may comprisecomputer-readable instructions which cause a computer, or morespecifically the processing unit 602 of the computing device 600, tooperate in a specific and predefined manner to perform the functionsdescribed herein, for example those described in the method 700.

Computer-executable instructions may be in many forms, including programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc., that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

The embodiments described herein are implemented by physical computerhardware, including computing devices, servers, receivers, transmitters,processors, memory, displays, and networks. The embodiments describedherein provide useful physical machines and particularly configuredcomputer hardware arrangements. The embodiments described herein aredirected to electronic machines and methods implemented by electronicmachines adapted for processing and transforming electromagnetic signalswhich represent various types of information. The embodiments describedherein pervasively and integrally relate to machines, and their uses;and the embodiments described herein have no meaning or practicalapplicability outside their use with computer hardware, machines, andvarious hardware components. Substituting the physical hardwareparticularly configured to implement various acts for non-physicalhardware, using mental steps for example, may substantially affect theway the embodiments work. Such computer hardware limitations are clearlyessential elements of the embodiments described herein, and they cannotbe omitted or substituted for mental means without having a materialeffect on the operation and structure of the embodiments describedherein. The computer hardware is essential to implement the variousembodiments described herein and is not merely used to perform stepsexpeditiously and in an efficient manner.

The term “connected” or “coupled to” may include both direct coupling(in which two elements that are coupled to each other contact eachother) and indirect coupling (in which at least one additional elementis located between the two elements).

The technical solution of embodiments may be in the form of a softwareproduct. The software product may be stored in a non-volatile ornon-transitory storage medium, which can be a compact disk read-onlymemory (CD-ROM), a USB flash disk, or a removable hard disk. Thesoftware product includes a number of instructions that enable acomputer device (personal computer, server, or network device) toexecute the methods provided by the embodiments.

The embodiments described in this document provide non-limiting examplesof possible implementations of the present technology. Upon review ofthe present disclosure, a person of ordinary skill in the art willrecognize that changes may be made to the embodiments described hereinwithout departing from the scope of the present technology. For example,trim values may be applied to VGM in order to optimize one or moreparameters of the engine concurrently. The engine may be a turbofan orturboprop instead of a turboshaft. The engine may have a single spoolinstead of multiple spools. The engine may have a single compressionstage or multiple compression stages. Yet further modifications could beimplemented by a person of ordinary skill in the art in view of thepresent disclosure, which modifications would be within the scope of thepresent technology.

1. A method for configuring at least one variable geometry mechanism(VGM) of an aircraft engine, the method comprising: obtaining pass-offtesting data for the aircraft engine, the pass-off testing dataindicative of an actual value of at least one operating parameter of theaircraft engine; determining, based on the pass-off testing data, atleast one trim value to be used to adjust a setting of the at least oneVGM to bring the actual value of the at least one operating parametertowards a target value, a running line of the aircraft engine beingsubstantially constant when the actual value of the at least oneoperating parameter is at the target value; and adjusting, duringpass-off testing of the aircraft engine, the setting of the at least oneVGM using the at least one trim value.
 2. The method of claim 1, furthercomprising: obtaining new pass-off testing data for the aircraft enginewith the setting of the at least one VGM adjusted using the at least onetrim value, the new pass-off testing data indicative of a new value ofthe at least one operating parameter; assessing, based on the newpass-off testing data, whether the new value of the at least oneoperating parameter is within a production acceptance range; adjustingthe at least one trim value when the new value of the at least oneoperating parameter fails to be within the production acceptance range;and retaining the at least one trim value when the new value of the atleast one operating parameter is within the production acceptance range.3. The method of claim 1, wherein the adjusting the setting of the atleast one VGM using the at least one trim value comprises applying theat least one trim value to at least one nominal schedule of the at leastone VGM to determine at least one trimmed schedule for the at least oneVGM, the setting of the at least one VGM adjusted in accordance with theat least one trimmed schedule.
 4. The method of claim 3, wherein the atleast one nominal schedule represents the setting of the at least oneVGM as a function of the at least one operating parameter, and furtherwherein the at least one trim value is applied to the at least onenominal schedule as a constant value for all values of the at least oneoperating parameter.
 5. The method of claim 3, wherein the at least onenominal schedule represents the setting of the at least one VGM as afunction of the at least one operating parameter and of at least oneadditional parameter, and further wherein the applying the at least trimvalue to the at least one nominal schedule comprises determining atleast one scaling factor to be applied to the at least one trim value toobtain at least one scaled trim value that accounts for the at least oneadditional parameter and applying the at least one scaled trim value tothe at least one nominal schedule.
 6. The method of claim 5, wherein theat least one operating parameter comprises at least one of a specificfuel consumption, a turbine inlet temperature, a surge margin, apressure ratio, and an acceleration time of the aircraft engine, andfurther wherein the at least one additional parameter comprises at leastone of an altitude, an ambient pressure, an ambient temperature, arotational speed of the aircraft engine, a power of the aircraft engine,and an air pressure measured at an exit of at least one compressionstage of the aircraft engine.
 7. The method of claim 1, furthercomprising: obtaining a virtual engine model for simulating a behaviourof the aircraft engine; running the virtual engine model to determine aposition of the at least one VGM at which the actual value of the atleast one operating parameter is brought towards the target value; anddetermining the at least one trim value based on the position of the atleast one VGM as determined.
 8. The method of claim 7, wherein therunning line is defined as a function of a first parameter and a secondparameter of the aircraft engine, and further wherein running thevirtual engine model comprises: aligning the virtual engine model withthe pass-off testing data to obtain an aligned model; running thealigned model to simulate the behaviour of the aircraft engine at atarget value of the first parameter; determining a first position of theat least one VGM at which a target value of the second parameter isachieved; determining a current value of a third parameter of theaircraft engine with the at least one VGM in the first position; runningthe aligned model to simulate the behaviour of the aircraft engine atthe current value of the third parameter to determine a second positionof the at least one VGM; and determining the at least one trim value bysubtracting the first position from the second position.
 9. The methodof claim 8, wherein the first parameter is compressor mass flow, thesecond parameter is one of pressure ratio and surge margin, and thethird parameter is one of shaft horse power and corrected compressorrotor speed.
 10. The method of claim 1, wherein the at least one trimvalue is determined for the running line of one or more compressionstages of the aircraft engine to be substantially constant, the at leastone VGM associated with the one or more compression stages.
 11. A systemfor configuring at least one variable geometry mechanism (VGM) of anaircraft engine, the system comprising: at least one processing unit;and a non-transitory computer readable medium having stored thereonprogram code executable by the at least one processing unit for:obtaining pass-off testing data for the aircraft engine, the pass-offtesting data indicative of an actual value of at least one operatingparameter of the aircraft engine; determining, based on the pass-offtesting data, at least one trim value to be used to adjust a setting ofthe at least one VGM to bring the actual value of the at least oneoperating parameter towards a target value, a running line of theaircraft engine being substantially constant when the actual value ofthe at least one operating parameter is at the target value; andadjusting, during pass-off testing of the aircraft engine, the settingof the at least one VGM using the at least one trim value.
 12. Thesystem of claim 11, wherein the program code is executable by the atleast one processing unit for: obtaining new pass-off testing data forthe aircraft engine with the setting of the at least one VGM adjustedusing the at least one trim value, the new pass-off testing dataindicative of a new value of the at least one operating parameter;assessing, based on the new pass-off testing data, whether the new valueof the at least one operating parameter is within a productionacceptance range; adjusting the at least one trim value when the newvalue of the at least one operating parameter fails to be within theproduction acceptance range; and retaining the at least one trim valuewhen the new value of the at least one operating parameter is within theproduction acceptance range.
 13. The system of claim 11, wherein theprogram code is executable by the at least one processing unit foradjusting the setting of the at least one VGM using the at least onetrim value comprising applying the at least one trim value to at leastone nominal schedule of the at least one VGM to determine at least onetrimmed schedule for the at least one VGM, the setting of the at leastone VGM adjusted in accordance with the at least one trimmed schedule.14. The system of claim 13, wherein the at least one nominal schedulerepresents the setting of the at least one VGM as a function of the atleast one operating parameter, and further wherein the program code isexecutable by the at least one processing unit for applying the at leastone trim value to the at least one nominal schedule as a constant valuefor all values of the at least one operating parameter.
 15. The systemof claim 13, wherein the at least one nominal schedule represents thesetting of the at least one VGM as a function of the at least oneoperating parameter and of at least one additional parameter, andfurther wherein the program code is executable by the at least oneprocessing unit for applying the at least trim value to the at least onenominal schedule comprising determining at least one scaling factor tobe applied to the at least one trim value to obtain at least one scaledtrim value that accounts for the at least one additional parameter andapplying the at least one scaled trim value to the at least one nominalschedule.
 16. The system of claim 15, wherein the at least one operatingparameter comprises at least one of a specific fuel consumption, aturbine inlet temperature, a surge margin, a pressure ratio, and anacceleration time of the aircraft engine, and further wherein the atleast one additional parameter comprises at least one of an altitude, anambient pressure, an ambient temperature, a rotational speed of theaircraft engine, a power of the aircraft engine, and an air pressuremeasured at an exit of at least one compression stage of the aircraftengine.
 17. The system of claim 11, wherein the program code isexecutable by the at least one processing unit for: obtaining a virtualengine model for simulating a behaviour of the aircraft engine; runningthe virtual engine model to determine a position of the at least one VGMat which the actual value of the at least one operating parameter isbrought towards the target value; and determining the at least one trimvalue based on the position of the at least one VGM as determined. 18.The system of claim 17, wherein the running line is defined as afunction of a first parameter and a second parameter of the aircraftengine, and further wherein the program code is executable by the atleast one processing unit for running the virtual engine modelcomprising: aligning the virtual engine model with the pass-off testingdata to obtain an aligned model; running the aligned model to simulatethe behaviour of the aircraft engine at a target value of the firstparameter; determining a first position of the at least one VGM at whicha target value of the second parameter is achieved; determining acurrent value of a third parameter of the aircraft engine with the atleast one VGM in the first position; running the aligned model tosimulate the behaviour of the aircraft engine at the current value ofthe third parameter to determine a second position of the at least oneVGM; and determining the at least one trim value by subtracting thefirst position from the second position.
 19. The system of claim 18,wherein the first parameter is compressor mass flow, the secondparameter is one of pressure ratio and surge margin, and the thirdparameter is one of shaft horse power and corrected compressor rotorspeed.
 20. The system of claim 11, wherein the program code isexecutable by the at least one processing unit for determining the atleast one trim value for the running line of one or more compressionstages of the aircraft engine to be substantially constant, the at leastone VGM associated with the one or more compression stages.